When servicing aircraft between flights, it is often necessary to refill toilet tanks with toilet fluid from trucks or other toilet-fluid sources. When doing this, an operator provides a pressurized source of toilet fluid at a toilet tank fitting nozzle to which the operator can couple the source. In this respect, the fitting is usually near a bottom of an aircraft fuselage, inside a service door or the like, which can be reached by an operator from outside the aircraft. However a toilet tank for storing the toilet fluid in the aircraft is located in a different place, the fitting being attached to the toilet tank via a pipe, hose, or the like. It is beneficial for the operator to be able to close a valve on the fitting in order to terminate flow of pressurized toilet fluid to the toilet tank when the toilet tank is full, as can be determined from within the aircraft, thus, most such fittings have levers, or the like thereon so that valves thereof can be selectively closed. However, such structure produces a problem in that the fitting and some of the pipe extending between the fitting and the toilet tank are exposed to outside temperatures. During winter and/or when the aircraft is flying at high altitudes, toilet fluid left in the fitting and in the pipe between the fitting and the toilet tank freezes, which can crack or split the pipe. Thus, it is an object of this invention, to provide an aircraft toilet tank filling valve assembly to be used as such a fitting which can be selectively closed by an operator, but which does not leave a residue of toilet fluid in the valve assembly nor in the pipe between the fitting and the toilet tank.
It has been suggested to solve this above-described problem by having a return bypass system in conjunction with a rotary ball valve system. That is, according to this suggestion, a bypass pipe is installed above the fitting with a one-way valve therein to allow fluid to automatically flow from the pipe between the fitting and the toilet tank back to a pipe feeding the fitting after pressure is removed therefrom. Such a bypass pipe, including a one-way check valve is rather cumbersome to use, labor intensive to construct and adds considerable weight to an aircraft. Therefore, it is an object of this invention, to provide an aircraft toilet tank filling valve assembly which does not retain residue water, which is relatively easy to construct, install and use and which does not add undue weight to an aircraft.